Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$197.83	4.589%	$206.9084	$206.91	$206.90	$206.90
Purchase #2	$99.94	5.446%	$105.3827	$105.38	$105.40	$105.40
Purchase #3	$224.36	11.815%	$250.8681	$250.87	$250.85	$250.90
Purchase #4	$244.86	8.742%	$266.2657	$266.27	$266.25	$266.30
Purchase #5	$223.69	4.737%	$234.2862	$234.29	$234.30	$234.30
Purchase #6	$115.51	13.699%	$131.3337	$131.33	$131.35	$131.30
Purchase #7	$194.58	13.113%	$220.0953	$220.10	$220.10	$220.10
7 purchase totals =	$1,300.77		$1,415.1401	$1,415.15	$1,415.15	$1,415.20